The prebiotic molecular inventory of Serpens SMM1: II. The building blocks of peptide chains

Niels F. W. Ligterink; Aida Ahmadi; Bijaya. Luitel; Audrey Coutens; Hannah Calcutt; Łukasz Tychoniec; Harold Linnartz; Jes K. Jørgensen; Robin T. Garrod; Jordy Bouwman

paper

The prebiotic molecular inventory of Serpens SMM1: II. The building blocks of peptide chains

arXiv:2202.09640

Abstract

This work aims to constrain the abundances of interstellar amides, by searching for this group of prebiotic molecules in the intermediate-mass protostar Serpens SMM1-a. ALMA observations are conducted toward Serpens SMM1. A spectrum is extracted toward the SMM1-a position and analyzed with the CASSIS line analysis software for the presence of characteristic rotational lines of a number of amides and other molecules. NH $_{2}$ CHO, NH $_{2}$ CHO $ν_{12}$ =1, NH $_{2}^{13}$ CHO, CH $_{3}$ C(O)NH $_{2}$ $ν$ =0,1, CH $_{2}$ DOH, CH $_{3}$ CHO, and CH $_{3}$ C(O)CH $_{3}$ are securely detected, while trans-NHDCHO, NH $_{2}$ CDO, CH $_{3}$ NHCHO $ν$ =0,1, CH $_{3}$ COOH, and HOCH $_{2}$ CHO are tentatively identified. The results of this work are compared with detections presented in the literature. A uniform CH $_{3}$ C(O)NH $_{2}$ /NH $_{2}$ CHO ratio is found for a group of interstellar sources with vast physical differences. A similar ratio is seen for CH $_{3}$ NHCHO, based on a smaller data sample. The D/H ratio of NH $_{2}$ CHO is about 1--3\% and is close to values found in the low-mass source IRAS~16293--2422B. The formation of CH $_{3}$ C(O)NH $_{2}$ and NH $_{2}$ CHO is likely linked. Formation of these molecules on grain surfaces during the dark cloud stage is a likely scenario. The high D/H ratio of NH $_{2}$ CHO is also seen as an indication that these molecules are formed on icy dust grains. As a direct consequence, amides are expected to be present in the most pristine material from which planetary systems form, thus providing a reservoir of prebiotic material.

Accepted for publication in ACS Earth and Space Chemistry; 59 pages, 10 figures